( BBC ) - Broadband speeds in the UK are much slower than advertised by internet service providers, a study by Computeractive magazine has found.
Some 3,000 readers took part in speed tests and 62% found they routinely got less than half of the top speed advertised by their provider.
It is the latest in a series of questions over the way net firms advertise broadband services.
Regulator Ofcom said it was aware of the issue and was "investigating".
Testing times
The figures were gathered from more than 100,000 speed tests that the 3,000 respondents carried out to build up a picture of their average net-browsing speed on ADSL lines.
Statistics about net users in the UK show that half of current broadband users receive ADSL services that should run at speeds between one and four megabits per second (mbps).
The other 50% are on deals offering up to eight mbps but the tests revealed that, in reality, very few achieve the top speeds.
"This problem has been building for a while with a growing gulf between what is advertised and what is delivered," said Paul Allen, editor of Computeractive.
"The adverts often have super-fast broadband in huge lettering with the "up to" clause in very small print," he said.
"Users who have taken the test were surprised at the size of the gulf," he added.
Some 28% of the 3,000 respondents who took the ADSL speed test found that they received less than a quarter of their maximum advertised bandwidth.
While consumers may currently not notice their sluggish connections, this could change thinks Mr Allen.
"Previously it has not been a massive issue but in the coming year we are entering the net TV age and video content is bandwidth-hungry," he said.
Mr Allen called on regulator Ofcom to provide an independent speed test to anyone who has signed up to receive broadband.
Speaking for the telecommunications watchdog, a spokesman said: "We are looking at this issue. It is not a huge driver of complaints but it has come on to our radar screen."
"It's about the difference between the headline rate and the rate received," he said.
The spokesman said Ofcom was working with the net industry and other organisations such as Which to investigate the extent of the problem and what can be done about it.
"Once we have carried out this work we will assess what options might be available to tackle it," he said. The results of the investigation would be made available in the "near future", said the spokesman.